1. Field of the Invention
The present invention relates generally to electroacoustic transducers employed in sonar systems, and more particularly to an electroacoustic transducer capable of accommodating multiple sonar beams which utilizes collimating acoustic lenses.
2. Description of the Prior Art
Sonar systems utilize narrow beams of sound energy projected in certain desired directions from a marine vehicle, and receive reflected energy from these directions, as described, for example, in U.S. Pat. No. 3,257,638, Doppler Navigation System, issued to Jack Kritz and Seymour D. Lerner in 1966. Conventionally, these beams are produced by vibrating piezoelectric discs with diameters that are large compared to the wavelength of the soundwave propagated or to be received. When multiple beams are utilized, the transducer assembly must be enlarged to accommodate the multiplicity of necessary elements. Multiple beam transducers of the prior art create installation difficulties, particularly on small ships, and provoke increased installation costs due to larger gate valves and stronger required structural supports. Thus, there is a need for relatively compact multiple beam transducers that will facilitate installation and mitigate attendant costs.
The Inventor's prior application, Ser. No. 354,973, filed Mar. 5, 1982, entitled Multiple Beam Lens Transducer For Sonar Systems describes a compact apparatus for transmitting and receiving multiple sonar beams. An acoustic lens directs plane waves incident in desired directions to electroacoustic transducers disposed in spherical shell segments centered in the focal regions of the lens associated with the incident beams. The electroacoustic transducers transmit spherical waves that are transformed by the acoustic lens to plane waves emergent in the desired directions.
The manufacture of this transducer entails some difficulty and expense resulting from the need to fabricate piezoceramic crystal elements in the form of spherical shell segments.